In 1961, typical necrotizing vasculitis occuring in tissues of patients with infectious processes due to Pseudomonas aeruginosa was recognized. These were recognized in 1965 to be associated with the elastase of these bacteria. Since that time there have been numerous publications on the elastase of P. aeruginosa. The elastase of P. aeruginosa was crystallized and it was found to contain 0.9 gram atom zinc per mole of the enzyme, which is essential to the enzymatic activity. The elastase has a molecular weight of about 35.000. It is most active in the neutral pH range and it is known to be inactivated by various metal chelators, the zinc being an essential component for its activity.
The elastase is inhibited by EDTA and O-phenanthroline. Certain peptide hydroxamic acids are effective inhibitors for this elastase. The known inhibitors are effective at rather large concentrations. According to the present invention there are provided highly specific inhibitors which are effective at very low concentrations and which can be used as the active ingredient in pharmaceutical, and especially ophthalmic compositions for the prevention of, and for the treatment of afflictions of the human eye by P. aeruginosa and for the treatment of other diseases caused by this microorganism or by microorganisms which produce a similar enzyme.